We're using observational astronomy to understand striking features of the cosmos, including the large-scale web of material in the Universe, supernovae, and the distorted appearance of distant galaxies.
Large scale structure
Large astronomical surveys measuring the positions of galaxies reveal a complicated large-scale structure within the observable Universe. Galaxies form where there are the highest concentrations of material in the Universe, so patterns of galaxies point to the physical properties of the early Universe.
As we look to more and more distant galaxies, we see further into the history of the Universe, seeing galaxies at earlier and earlier times. By comparing the patterns of galaxies, we can uncover information about how much the Universe has grown.
Our research into the large scale structure proves that the expansion of the Universe is accelerating. From our research, we can obtain information on the exact form of this acceleration.
Within the University's Institute of Cosmology and Gravitation, our researchers are involved in astronomical survey projects that are advancing what we know about galaxies in the Universe, and helping to solve the mystery of dark energy.
Astronomical survey projects we're involved in are:
30th Texas Symposium on Relativistic Astrophysics
The 30th Texas Symposium on Relativistic Astrophysics will take place from Sunday 15 to Friday 20 December 2019 in the historic seaside city of Portsmouth, UK, hosted by the University of Portsmouth’s Institute of Cosmology and Gravitation (ICG).
The Texas meetings have covered topics such as black holes, gravitational waves, neutron stars, cosmic rays, dark matter and the early Universe since the first symposium, held in Dallas in 1963. Following the tradition of previous meetings, the 2019 Symposium will cover a broad range of subjects in relativistic astrophysics.
For full details please visit the Texas 2019 conference website.
It's often assumed that light travels in a straight line, but light can be bent by the effects of gravity in the Universe.
Wherever there is a clump of matter, there is a slight distortion of space and time – the light that passes is deflected. This bending of light is called ‘gravitational lensing.’ This leads to striking images of distant galaxies that appear to be stretched and magnified.
We research the appearance of these galaxies to understand the source of gravitational lensing, and to see what amounts of lensing can tell us about the behaviour of gravity itself. We expect the source of lensing to be the dark matter between us and the galaxies.
Supernovae are some of the most energetic events in the Universe – mostly caused by the chaotic end-stage of a dying star. We're specifically interested in one type, called a Type Ia Supernova (SNela), believed to be the thermonuclear explosion of a white dwarf star.
SNela are some of the brightest supernovae in existence and can be seen from great distances. Their brightness can be standardised, making them ideal cosmological probes.
In 1999, two groups of astronomers used distant SNela to measure the expansion rate of the Universe. They made an amazing discovery: expansion was accelerating, not slowing as expected. This discovery –which earned Saul Perlumutter, Brian P. Schmidt, and Adam G. Riess the 2011 Nobel Prize in Physics – is believed to be driven by dark energy, a gravitationally repulsive substance taking up about 70% of the Universe.
Our researchers are involved in two major searches for new SNeIa:
- Sloan Digital Sky Survey (SDSS) Supernova Survey – Cosmologists in our Institute of Cosmology and Gravitation have used the SDSS to extend our understanding of SNeIa through their rate of collapse, their correlations with the host galaxy, and by using techniques for performing photometric classification of SNeIa, which will be essential for future surveys.
- Dark Energy Survey Supernova Survey (DES) – In September 2013, the DES Survey began, using the 520 Megapixel Dark Energy Camera (DECam) on the Blanco Telescope in Chile. By surveying 30 square degrees of sky, DES is expected to find thousands of new SNeIa, increasing the number of known events by at least a factor of five. DES aims to improve the photometric measurements of each supernova and is expected to improve our knowledge of supernova astrophysics through detailed studies of their rate of collapse and global properties. DES will find new phenomena such as superluminous supernovae which appear to be up to 100 times brighter than normal SNeIa.
Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy samples (2014), Lado Samushia, Beth A. Reid, Martin White, Will J. Percival, Antonio J. Cuesta, Gong-Bo Zhao, Ashley J. Ross, et al.
Measuring growth rate and geometry with anisotropic clustering (2014), Lado Samushia, Beth A. Reid, Martin White, Will J. Percival, Antonio J. Cuesta, Gong-Bo Zhao, Ashley J. Ross, et al.
No Detectable Colour Dependence of Distance Scale or Growth Rate Measurements (2013) Ashley J. Ross, Lado Samushia, Angela Burden, Will J. Percival, Rita Tojeiro, et al.
Baryon Acoustic Oscillations in the Data Release 9 Spectroscopic Galaxy Sample (2012), Lauren Anderson, Eric Aubourg, Stephen Bailey, Dmitry Bizyaev, Michael Blanton, Adam S. Bolton, et al.
Anti-lensing: the bright side of voids, Phys. Rev. Lett. 110, 021302 (2013), Krzysztof Bolejko, Chris Clarkson, Roy Maartens, David Bacon, Nikolai Meures, Emma Beynon
Probing modifications of General Relativity using current cosmological observations, Phys.Rev.D81:103510,2010, Gong-Bo Zhao, Tommaso Giannantonio, Levon Pogosian, Alessandra Silvestri, David J. Bacon, Kazuya Koyama, Robert C. Nichol , Yong-Seon Song
Weak lensing predictions for modified gravities at non-linear scales, Mon. Not. R. Astron. Soc. 403, 353-362 (2010), Emma Beynon, David J. Bacon, Kazuya Koyama
Complementarity of Weak Lensing and Peculiar Velocity Measurements in Testing General Relativity, Phys.Rev. D84 (2011) 083523, Yong-Seon Song, Gong-Bo Zhao, David Bacon, Kazuya Koyama, Robert C Nichol, Levon Pogosian
Discover our areas of expertise
We're detecting cosmic gravitational waves and developing gravitational-wave observations as an astronomical tool.
We're exploring the inflation of the very early Universe, the impact of dark energy on its geometry and developing tests to monitor its expansion.
Interested in a PhD in Cosmology & Astrophysics?
Browse our postgraduate research degrees – including PhDs and MPhils – at our Cosmology & Astrophysics postgraduate research degrees page.